This essay was originally published in August of 2002. While conservation measures have extended the life of the NANP and exhaust is now more than 40 years away, two generations from now a change will be needed. This section remains to express my opinion on how that change can be made.

There is an official plan - this is not the official plan.

Expanding the NANP

Up to this point the North American Numbering Plan (NANP) has worn well. Designed in the 1940's and introduced to subscribers in the 1950's and 60's the numbering format is basically the same as when it started: A 10 digit number divided into three groups; a three digit area code (or Number Plan Area), a three digit exchange code, and a four digit line number.

Dialing plans have changed over the years with many different dialing codes being replaced by the familiar 1+ and 0+ codes that most use today. In addition, some areas use 7D and 10D numbers directly based on local rules, but these dialing plans do not break the basic numbering plan "3-3-4" that has survived since the 40's.

But as it seems there is no end to the need for numbers, expansion to longer than 10D numbering is needed. When is a moving target, some say 2010 and others say 2050, but the day will come when something other than "3-3-4" will be required.

Expansion Needs
There is a generally recognized need for more exchange codes within each area code. That is the reason for most NPA relief, adding more available exchange codes. It makes sense to use the expansion of the NANP to more than 10D to add more exchange codes to each NPA. Therefore the length of the exchange code portion of the number should be extended to four digits.

In addition, even with an 8 to 10 fold increase in exchange codes, adding to the number of available NPAs (area codes) is also desired. The length of the NPA portion would be extended to four digits, giving a full 12D number.

While it is not immediately apparent what we will do with such a huge increase in numbering space, moving directly to 12D will save changing numbers twice. The NANP has a good history of long lasting numbering plans, I do not wish the expansion be any less short lived.

Flag Day is June 14th in the US. That is my only need to use the term. A telephone flag day should be avoided. Too much equipment needs to be cut over to do it on one day, both telephone system and subscriber equipment. The plan should not have a flag day switch.

International presentation should also be easy. Writing +1 npa-nxx-xxxx works great now, writing +1 npax-dnxx-xxxx will work in the future. International dialers will dial their access code (00+ or 011+) then the NANP country code (1) then the 12D number. NANP callers will dial an access code (1 - very similar looking to the country code) then the 12D number.

[I have seen some options that appear to extend the numbering to 12D but they only have 11 significant digits. That should be avoided. If your area code is 219 it should be expressed "219", not a fake "1219". The leading 1 is a dialing code, not part of the numbering system. My plan is similar to what NANP users have now, real numbers where every digit is significant and dialing codes to tell the phone company how much of the number the subscriber is using.]

Expansion Options
"Sent Paid" is currently 1+10D, that will change to 1+12D with the note that 1+ dialing will always reach the correct destination (and be billed correctly). There are shorter dialing codes such as 10D in overlays and 7D which reaches either a number in your area code or a number that is local depending on local custom. In most cases both 10D and 7D dialing will be migrated to 8D (there will be differences in the non-US portions of the NANP). Charging will not be affected by the numbering changes. Areas with toll-alerting will be able to keep it, areas without toll-alerting will be able to keep their system.

The idea is to make the change as painless as possible for all users, not to force the entire NANP to some 'preferred' system that is only truely needed in another area.
What Will Be Lost?
Every plan has a loss, the loss chosen for this plan is to drop 0+ Operator Assisted dialing. Much of this usage has moved to 1-800 numbers. The benefit of having 0+ available for other uses outweighs the loss. For those who wish to keep dialing 0+, a replacement code of 001+ will be made available - adding two digits to Operator Assisted without losing the feature.

In exchange subscribers in the US will get 8D dialing ... one more digit at the beginning of their call that in most cases will prevent them from needing to dial 1+ the full 12D number. Initially that one digit will be the "0", but as exchange use need grows there will be new four digit exchanges in the 2-9 range. (In overlay areas where overlaid codes are being recombined into a single new 4D NPA that number will not be "0", local plans will be made. Also by choice Canada will not be forced to 8D dialing, nor will the remainder of the non-US NANP.)

Mitigating the Damage
EVERY proposal to extend number length will cause a certain amount of stress and expense to every person in the NANP. Everyone will need new stationary, new signs, and new thought to recognize the new 4D NPA numbers and 4D exchanges as theirs.

To assist in this, Canada will move all of their NPAs to +1 00 plus 10D. The 12D NANP numbers for Canada will all start 00 and have their current 10D number following. In the dialing pattern, the Canadian numbers will be reached by dialing 100+ the old 10D number instead of 1+10D.

The non-US/Canada NANP will also move en-block to the +1 99 plus 10D range. There have been enough complaints about these codes being mixed in with domestic numbers in both the US and Canada. They deserve their own numbering space. In addition, this prevents these countries from needing to change their NPAs to any patterns that would lose special spellings.

The US will make the most changes. Most NPAs will follow the 'insert 9' pattern, placing a nine as the second digit, (npa -> n9pa) eg: 219 would become 2919. A zero being added at the beginning of the exchange code leads to the simple:
npa-nxx-xxxx -> n9pa-0nxx-xxxx

In overlay areas that choose to recombine the same 4D NPA will be chosen for all areas. The exchange codes will have a DIFFERENT number added to the beginning. In addition some splits may be recombined. For example, in Chicago they might recombine the 312/773 split: (rough example)
312-nxx-xxxx -> 3912-2nxx-xxxx
773-nxx-xxxx -> 3912-3nxx-xxxx

Simple to recognize patterns will help, but to further help with 'damage control' a special access code "10"+ will be introduced for transition. By dialing 10+ the old 10D number your call will go through. This "Ten plus Ten Digits" transition dialing would become an interrupt about a year after the new 4D NPAs were in place and will function as a stress relief. The former 1+10D numbers will also remain in use during transition, however the plan is to leave the 10+10D intercepts in place for as long as the system demands no other use (10 years would be a good minimum). Note that 10+ a current NPA does not interfere with the use of 101+ Carrier Access Codes.

In addition, 00+ will be permitted for "Sent Paid International" right alongside the current 011+ "Sent Paid" and 01+ "Operator Assisted". This is to aid international visitors.

The next few pages will explain (with some repitition) the logic and transition process. You can cut to the review if you wish, but don't say I didn't offer an explanation!

[Introduction] - [Moving 7D -> 8D] - [12D Plan] - [Transition] - [Complete Review]

The Official Plan
While the migration to longer than 10 digits remains decades away there is an official plan that has been accepted by the industry. Some of the concepts presented above were rejected in the official plan.
  1. Separating the countries. Creating +100 for Canada and +199 (or another separation) for non-US countries was rejected as it was seen as breaking up the North America Numbering Plan and ran contrary to a goal of having a unified plan.
  2. Inserting a 9. Adding a second digit was built in for expansion when the NANP was last expanded (allowing 2-8 as a second digit of an area code). 9 as a second digit was reserved for any expansion plan similar to mine above that used that digit to determine whether the call was to a three digit area code or a four digit area code. Removing this restiction will extend the life of 10 digit dialing. The industry felt "insert a 9" was too confusing for users.
  3. Canada. Canada still wants a flag to denote a "Canadian" area code. Discussions ended offering adding a zero to the end of Canadian area codes and a one to the end of non Canadian area codes.
  4. The plan. Two digits, either 00, 01, 10 or 11 will be added between the area code and existing local number. The first digit will extend the area code to four digits (NXX becomes NXXX) and the second digit will extend the local exchange to four digits (NXX becomes XXXX). This plan takes into account the restriction on the "D" digit ... the fourth digit of a telephone number cannot be 0 or 1. Removing that restriction and using fourth digit 0 or 1 to determine three digit vs four digit area code (and subsequent local exchange code) provides a smooth transition.
  5. Phasing. The plan allows for an option of expanding the number of NPAs separate from expanding the number of local exchange codes. If the expansion is phased the phases will be decades apart.